The invention is concerned with an arrangement for sealing the guide pin of a floating-caliper spot-type disc brake. The guide pin is fastened to the brake carrier member to join the carrier member to the brake caliper member. The guide pins are slidably received in an opening of the brake caliper member and threadedly connected to the brake carrier member. A sealing boot is retained at the open rim of the caliper member opening at its one end and tightly embraces the pin with its other end. A bellows portion of the boot interconnects both ends.
In a known disc brake of this type (German printed and published patent application No. 27 30 338), a sealing ring is fastened at the open rim of the opening, the internal circumference of said sealing ring having the shape of an elastically yielding lip seal which is tightly applied to the external cylindrical surface of the guide pin. An annular flange is provided at the guide pin outside the opening and the lip seal. The surface of the lip seal engages a portion of the sealing ring located at its opposite end.
However, experience has shown that the known arrangement of sealing means is not capable of permanently protecting the guide pin against the penetration of moisture and dirt.
Indeed, it has already been proposed (German patent specification No. 29 02 378) to shape the sealing boot as a bellows portion and to stiffen its ends with lip sealing rings by metal rings embracing that portion. However, that boot design has the disadvantage of not being suitable for spot-type disc brakes whose caliper members are being swivelled around one of the two pins for a change of the pads because the bellows portion is not sufficiently flexible for this purpose.